As the final reader you're expected to do some due diligence and at the bare minimum read the reference list. Once you do, you can easily see which papers are self citations and which ones are not. If you're not doing this due diligence you probably don't care too much about this paper anyway and there is no harm done if you think a reference is not a self citation when it actually is.
That doesn't help if references are given as First Author et al. or even as [number] and while I agree in principle it simply doesn't happen in practice.
But then it just weakens your statement to make it worse. And I'm not even sure if it makes a difference for what the article talks about. Because the reviewer needs to actively go looking. And at least to my understanding these effects are not due to people going out of their way to misjudge people, but rather that it's an effect of subconscious prejudices. And for the latter breaking the obvious connection is probably enough.
